This grant proposal is a continuation of the program for the systematic study of psychotropic drugs on the Children's Service of Bellevue Psychiatric Hospital, New York. We plan to concentrate our efforts on preschool-age schizophrenic and autistic children. We wish to evaluate new drugs which may be potentially useful for these severely disturbed children, to carry out controlled studies of drugs which appear therapeutically promising, and to coordinate behavioral and biological changes on and off drugs. This will include further explorations of the therapeutic efficacy and safety of thyroid and thyrotropin - releasing hormones, as well as investigations of central nervous system (behavioral) - thyroid interrelationships in this population. Individual patients will be followed longitudinally to evaluate long-term outcome of drug treatment and somatosexual maturation. The studies will be carried out in order to develop a more rational approach in pharmacotherapy for this population of children, to delineate biologically more meaningful diagnostic categories or subgroups and define "drug responders."